Notch a board or a flat piece of bark. To make a bow, stretch a string between the ends of a flexible branch and tie it in place, then use a second stick as a vertical spindle. Place the spindle inside the bow with one end in the notched base. Turn the bow once to loop the string around the spindle, then hold the spindle's other end in place with a stone. Place a leaf under the notch and saw back and forth to create a coal. Then move it to the tinder bundle, and blow gently into flame.